Paper for toweling and other purposes



Patented Apr. 13,1937

PAPER FOR TOWELING AND o'rnna PURPOSES MiltonO. Schur, Berlin, N. H., assignor to Brown Company, Berlin, N. H., Main a corporation of No Drawing. Original application April 6, 1931,

Serial No. 528,229. Divided and this application August 30, 1935, Serial No. 38,575

8 :Claims.

This invention relates in its fundamental aspect to papers of high water absorptivity and yet possessing such a high degree of tenacity or integrity while wet as to resist effectively disintegration when put to such service'as toweling, in which capacity it can undergo more than usual or even vigorous manipulation without going to pieces.

More specifically, the subject of this invention 10 is paper toweling made of any suitable cellulose pulp as the raw material. One of the disadvantages incident to the use of the usual paper towels, for instance, even those made of such strong chemical wood pulp as kraft, is their tendency to disintegrate under the wiping action of wet hands. This disadvantage arises from the fact that the ordinary paper towels are of waterleaf variety, that is, contain nothing besides the cellulose pulp. The use of papermaking ingredients, such as sizes and binders, in paper towels has been abstained from, since it has been taken for granted that they detract from the capacity of the towels to absorb water. Generally speaking, this abstinence from the use of sizes or binders is sound practice, since the water absorbing capacity of paper towels is as important, if not more so, than the wet strength of such towels.

I have now discovered that the controlled use of glue or gelatine, especially in tanned condition, in paper toweling may be of remarkable advantage, since this particular sizing agent has the ability of vastly appreciating the wet strength of paper toweling while depreciating its water absorbency comparatively little. In accordance with the present invention, glue or gelatine is distributed through paper toweling in such a Way that the finished article absorbs water like similar waterleaf toweling but is far more resistant to disintegration especially while wet. The advantage of using glue in, paper toweling obtains up to a glue content of only about based on the dry weight of fiber, since when this maximum percentage is overstepped considerably, the increase in wet strength attributable to such overstepping is more than outweighed by the undesirable drop in water absorptivity. By remaining within an upper limit of about 5% glue content in the toweling, it is possible to achieve a multifold increase in the wet strength of the toweling over its waterleaf wet strength without much decrease'in its water absorptivity. This multifold increase in the wet strength of the towel is more than is necessary to render the towel resistant to disintegration even when put to vigorous use in the wiping of wet hands. Accordingly, there is no particular point in exceeding in the towel the limiting value of glue content mentioned, since the excess simply makes for greater expense and an impairment of the ability of the towel to imbibe water.

While there may be various ways of incorporate ing the desired amount of glue in paper toweling, a simple procedure open to ready application in usual papermaking practice devolves about start ing with a waterleaf web of toweling as it is re moved in partially or completely dried condition from the dry end of a paper making machine. The web of toweling may be composed of,'say,

kraft pulp, and possess a basis weight of, say, 37

pounds or thereabout. Assuming that one starts with a perfectly dry waterleaf web, the web may be passed through an aqueous glue solution whose glue content corresponds with that desired in the finished toweling. For instance, I may pass the web through an impregnating solution containing up to about 5% glue solids and preferably containing up to about /2% of a tanning agent such as formaldehyde, alum, or tannic acid. The solution-soaked web is then passed through squeeze rolls which may be adjusted to reduce the solution content of the web to a point where the Web holds its own weight of solution and thus has a glue content, based on fiber, similar to that of the impregnating solution. The squeezed web is then dried as by passage over a bank of drum driers similar to those used at the dry end of the usual paper machine. The dry toweling is characterized by an amazingly enhanced wet strength and a water absorptivity practically similar to that of the water-leaf paper used as a raw material. Indeed, the finished toweling containing only about 3% tanned glue, based on the weight of dry fiber, may be characterized by a wet strength about four to seven times as great as that of the waterleaf paper used as the starting material.

In the commercial application of my invention,

' the web of toweling may undergo such operations as creping and/0r embossing in the course of its manufacture, which operations. are well known in paper towel manufacture. If desired, the dried, glue-impregnated web may be mechanically softened, as by being broughtinto facial engagement, while under tension with the edge of a so-called doctor blade. The softness and Harpness of the web may also be enhanced by adding a. softening agent, such as glycerine,'soap, and alcohol, in relatively smallv amount to the glue solution. If desired, the glue solution may contain a small amount of suitable preservatives. for

instance, phenolic compounds of the type of sodium-ortho-phenyl-phenate, which permit the glue solution to stand for comparatively long periods without putrefaction.

5 The glue used as a raw material may be derived from various sources, such as bones, fish, or hides. The usual glues of commerce, including those which have heretofore sometimes been used in sizing papers, may serve as the raw material.

In fact, any of the glues on the market, glues which have been chemically treated or purified so as to be more valuable for use in paper toweling, and glues which upon drying become substantially water-insoluble, may be'selected for the purpose of my invention.

In accounting for the results which I secure, one should look to the structure or textures of the original water-leaf web and to the properties of the glue; especially in its state of distribution through the fibrous structure 'of the web. To begin with,the waterleaf web is made up largely of void spaces or pores rather than solid fibers. Even after the web has undergone impregnation with the glue solution and drying as heretofore described, it still possesses substantially its original volume of void spaces or pores. The small amount of glue incorporated through the web evidently forms exceedingly thin films or coatings on the individual fibers; and these thin films or coatings bind the fibers together with such tenacity at their regions of contact as to increase enormously resistance against separation of the fibers especially in the presence of water. Nevertheless, the glue,-even when'it is set in substantially water-insoluble condition, is apparently very easilywetted by water, by which I mean that water spreads easily over the films or coatings of glue rather than being shed therefrom. Inasmuch as the glue is distributed throughout the 40 web and is present in such small amount that a large overall glue surface is exposed to contact with water without material loss in the total volume of the pores, the web of necessity must have a large capacity for water absorption. Doubtless, too, in addition to being wetted by water, the

glueadsorbs and/or absorbs the water and then transmits water to the cellulose fibers, which, of course, are also capable of absorbing large amounts of water. Whether or not the foregoing explanation is accurate, insofar as concerns the structure .of the towels of the present invention and the actions ensuing from their use, it me, fact that by following the procedure hereinbefore outlined, it is possible to produce paper towels whose wet strength is surprisingly high and whose waterabsorptivity compares favorably with similar waterleaf toweling.

I am aware of the fact that it has been proposed to treat paper locally withglue or other agents for the purpose of reinforcing it against disintegratie 1 under the action of water, but the incor- .poration of glue as a continuous phase throughout the body of a waterleaf paper web, as hereinbefore described, possesses important features 01 superiority. To begin with, it is a relatively into and diffuses throughout the paper. Indeed, as already stated, the glue solutions which I employ should be used at a glue content not exceeding about 5%, as solutions of higher solids concentration are likely to clog the surface poresand thereby interfere with a uniform impregnation of .the waterleaf paper web; and even when they are suiliciently fluid to become uniformly distributed throughout the web, the web will retain more than the desired amount of glue. This 10 is attributable to the fact that, once the glue solution has entered uniformly into the web, the web tends to retainapproximately its own weight of glue solution, even after being thoroughly squeezed. l

I am not unmindful of the fact that in the early days of paper manufacture, glue alone was sometimes relied 'upon as a sizing material. In such case, however, the glue was used primarily to enhance the dry strength of the paper and to 20 prevent the spread of ink thereon. The ink-resisting quality desired in the paper was realized by filling the pores of the paper substantially entirely or largely with the glue substance, even though increase in strength'of thepaper began 25 with the addition of only small quantities of glue and progresively increased as the amount of glue increased and the pores of the paper were filled.

The desired filling of the pores of the paper and the attendant high strength and inhibition of the days of papermaking, to air-dry or loft-dry such 49 paper under conditions permitting unrestrained shinkage and the accompanying closing of the pores in the paper. With the advent of heater or rosin-sizing, it became the practice to size the paper pulp to'a considerable extent in the beater" 45 engine by disseminating rosin size throughout the pulp and then adding alum or other suitable precipitant to fix the rosin on the pulp fibers. The sized pulp was then run off on a papermaking machine. When papers of unusually high 50. strength and resistance to the spread ofink are currently demanded, a pre-sized'and'dried paper sheet is sometimes passed through a bath of sizing agent, such as a glue or starch solution, and redried. The second or surface-sizingtreatment 55 more perfectly fills the surface pores of the paper.

All the paper-sizing procedures of the prior art, including the sizing of paper with glue, werethus carried out so as to produce papers of low waterabsorptivity. e0

. It came as a distinct surprise to me that av waterleaf paper might be impregnated with-glue in such amount that its water absorptivity remained unimpaired while its wet strength under-' went a multifold increase, particularly when the 05. paper so impregnated was dried with shrinkage largely restrained, as is common practice on drum driers of the usual paper machine type. The value of my invention as applied to paper towel manufacture was therefore substantiated repeat- I edly' in order to make certain that accidental or fortuitous reasons were not responsible for the fruitful results initially secured.

I am using the expression glue in the specification and in the 'appended claims notonly in 7 the generic sense hereinbefore indicated, but also to include nitrogenous of protein glues, such as casein glues or glues prepared from albumens, for example, blood albumen, to all of which the principles of the present invention may extend.

So far as concerns subject-matter, this application is a division of my application Serial No. 528,229, filed April 6, 1931, wherein I have claimed a method of producing the paper product herein claimed.

I claim:

1. An article of the character described comprising a thin sheet of paper composed substantially of cellulose fibers in open formation, the fibers 15 throughout the sheet being substantially enveloped by only thin films of soft albuminous adhesive which is temporarily water-resistant for a substantial period, said films bonding together.said fibers at their regions of contact and the interstices between the thus bonded fibers being open, whereby the article is characterized by thinness, softness, flexibility, porosity and high wet strength.

2. A sheet of creped paper characterized by cellulose fibers in open formation, the fibers throughout the sheet being substantially enveloped by only thin films of albuminous adhesive and softening agent which is temporarily water-resistant for several hours, said films bonding together said fibers at their regions of contact and the interstices between the thus bonded fibers being open, whereby the article is characterized by thinness, softness, flexibility, porosity, and high wet strength.

' flexibility, porosity and high wet strength.

4. An article of the character described comprising a thin sheet of paper of open formation, the fibers throughout the sheet being substantially enveloped by. only thin films of albuminous adhesive, said films bonding together said fibers at their regions of contact and the interstices between the thus bonded fibers being open, said ad-- hesive being lnsoiubilized to make it water-resistant and comprising a proportion of softener, whereby the article is characterized by thinness. softness, flexibility and high wet strength.

5. As an article of manufacture, a paper product characterized by its water-absorbency and high wet-strength and comprising a paper base of porous fibrous structure substantially all of whose fibers are coated and bonded together at their regions of contact by only such thin films of albuminous adhesive as to preserve high residual porosity in said structure, said adhesive being in sufliciently water-insoluble condition to render said structure resistant to disintegration while wet.

6. As an article of manufacture, a paper product characterized by its water-absorbency and high wet-strength and comprising a paper base of porous fibrous structure substantially all of whose fibers are coated and bonded together at their regions of contact by only such thin films of glycerinated albuminous adhesive as to preserve high residual porosity in said structure, said adhesive being in sufilciently water-insoluble condition to render said structure resistant to disintegration while wet.

7. As an article of manufacture, a paper product characterized by its water-absorbency, and high wet-strength and comprising a paper base of porous fibrous structure substantially all of whose fibers are coated and bonded together attheir regions of contact by only such thin films of albuminous adhesive as to preserve high residual porosity in said structure, said adhesive being present in amount up to about 5%, based on the 1 weight of dry fiber, and in sufliciently waterinsoluble condition to render said structure resistant to disintegration while wet.

8. As an article of manufacture, a paper product characterized by its water-absorbency and high wet-strength and comprising a paper base of porous fibrous structure substantially all of whose fibers are coated and bonded together at their regions of contact by only such thin films of glycerinated albuminous adhesive as to preserve high residual porosity in said structure, said adhesive being present in amount up to about 5%, based on the weight of dry fiber and in sumciently water-insoluble condition to render said structure resistant to disintegration while wet.

MILTON O. SCHUR. 

